EAGER: Improving Lifetime and Data Reconstruction Time of Flash-Based RAID by Orchestrating Control between RAID and SSD Controllers

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To meet stringent latency and throughput requirements for big data applications, flash-based Solid-State Drive arrays (SSAs) have become popular in enterprise storage systems. SSAs have many advantages over conventional Hard Disk Drives (HDD), such as enhanced input/output (IO) performance and storage density, lower power, cooling, and rack space cost. However, SSAs have lower endurance and lower lifetime than HDDs, requiring more frequent replacement, negating some of their advantages.To optimize the lifespan of SSAs, this project will divide data into two separate classes, hereafter described as ordinary data and approximate data. With approximate storage, bad blocks that contain pages with uncorrectable errors can be reused to store approximate data that can tolerate some errors. Applying approximate storage in SSAs requires new mechanisms and techniques to coordinate redundant arrays of inexpensive disks (RAID) and SSD controllers to manage both approximate and ordinary data. This project will (1) develop new mechanisms to orchestrate control between RAID and SSD controllers to extend the lifespan of SSAs; (2) investigate new schemes to utilize the computing power of SSDs to accelerate the data reconstruction of SSAs under heavy workloads; and (3) integrate the above two approaches to develop an experimental framework for evaluation. This project is expected to have a major impact on industry, since it addresses a real, very timely technical problem. Further, this project has societal benefits, in reducing storage cost at data centers, educating graduate and undergraduate students about cloud computing architecture, while seeking to broaden participation of students from diverse backgrounds.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.